Geoengineering, Marine Microalgae, and Climate Stabilization

In 2010, estimated greenhouse gas emissions from human activities totaled nearly 46 billion metric tons worldwide (PDF Download), a 35 percent increase from 1990. Steadily building up in the atmosphere, they cause dangerous interference with the climate. The December 2015 Paris Climate Accord set a goal to limit average increases in temperature to 1.5 or 2 degrees C relative to pre-industrial levels to avoid catastrophic change. But at this point the world can no longer reach that target by merely reducing anthropogenic emissions. “To achieve climate stabilization, we also have to figure out how to remove carbon dioxide from the atmosphere,” says Charles Greene, Professor of Earth and Atmospheric Sciences at Cornell University, New York. A member of the Marine Algae Industrialization Consortium (MAGIC), which is led by Duke University in North Carolina, Greene recently co-published a paper in Earth’s Future (DOI: 10.1002/2016EF000486) detailing how the industrial production of marine microalgae can help accomplish this. “We present an economically viable way to reduce emissions and to capture and store atmospheric carbon, says Greene. “It is an integrated approach that addresses a series of critical global issues at once.”

Increasingly, scientists and policymakers are recognizing the urgency to remove atmospheric carbon dioxide. Geoengineering technologies are being proposed. But significant environmental and economical concerns have hindered their development. A technique known as Bioenergy with Carbon Capture and Storage (BECCS) has piqued interest in this field as well. The idea is to grow terrestrial crops for biofuel, then to capture and store the carbon dioxide when they are burned in power plants. But these crops compete with food crops for water, nutrients, and agricultural land, which has already been leading to large-scale deforestation. Forests are magnificent living systems for carbon capture and storage. Forests changed for agricultural use are currently causing about 20 percent of global carbon emissions.

So how can marine microalgae make a difference? “Rich in oils, marine microalgae grow ten to one hundred times faster than the fastest-growing terrestrial plants, so their production requires only a fraction of the land a terrestrial crop might need. It can even be non-arable land,” explains Greene. “If we can produce algal biofuel to scale, the climate benefits we gain from reducing land use may outweigh the benefits from the biofuel itself.”

Biofuel as a product may not even be the algae’s most important use. While algae’s carbon neutral, energy-dense fuels will likely be necessary to power ships, aircraft, and heavy vehicles, by mid-century they may be unnecessary for light vehicles, due to electric vehicles and solar energy taking off. However, beyond fuels as a use, algal biopetroleum could be used for other products such as plastics that traditionally are made from fossil-based petroleum. “These products would lock up carbon dioxide for the long term, removing it from the atmosphere. They can be used in humanity’s rapidly expanding built environments, our homes, even our cars. They can generate revenues offsetting the costs of industrial-scale algae production,” says Greene.

The MAGIC team is working to resolve some remaining challenges. For example, the industrial production of marine microalgae requires open-air ponds, where the algae must absorb enormous amounts of carbon dioxide in short amounts of time. But atmospheric carbon doesn’t diffuse fast enough through the pond layer where ambient air and surface water meet. “We are looking at ways to enhance diffusion,” says Greene. The algae also require large amounts of nutrients, especially phosphorus. Here, MAGIC currently envisions that algae cultivation may contribute to the development of large-scale wastewater treatment systems.

The integrated approach described in Earth’s Future summarizes a series of studies conducted under MAGIC’s predecessor, the Cornell Marine Algae Biofuels Consortium. The team’s researchers have regrouped under MAGIC, which formally launched in February 2016 with funding through the U.S Department of Energy, to discover what it takes to go to commercial scale. “We have come a long way,” says Greene. “When we started in the early 2000s, we were looking at fuels only. We found that food is critically important to make fuel viable, that you can produce enormous amounts of food, and that the approach delivers beneficial land-use changes. Rigorous assessments and modeling studies can now guide marine microalgae work forward to help in achieving climate stabilization.”